Low-power self-refresh (LPSR) is a power-saving mode devised for solid-state drives (SSDs) that consumes little power (e.g., approximately 2-5 milliwats (mW)) yet guarantees fast wake-up (e.g., approximately 70 ms round-trip). In the LPSR mode, the SSD is transitioned to a low-power state, where the SSD's dynamic random-access memory (DRAM) supplies remain powered-on while all other supplies (including negative-AND (NAND) supplies) are powered-off. Generally, a certain number of NAND power-cycles (e.g., a maximum of ten million power-cycles) can be performed during the lifetime of the SSD without compromising data retention or consistency.
Typically, the LPSR mode activates when the SSD has been idle for a certain amount of time in order to amortize the entry/exit power cost as well as to ensure low latencies when carrying out input/output (I/O) requests. According to some approaches, a timer is set to a fixed time period or idle interval (e.g., five seconds) and the LPSR mode activates when the timer elapses. Unfortunately, this technique provides no control over the LPSR idle interval and does not take into account a rate at which the NAND power-cycles are consumed, which can result in inefficient power management and faster wear out of the NAND based on the nature of the workload.